Edward CastronovaYesterday, Facebook killed its virtual currency. (Thanks Travis Ross for the heads up.) However, the payment systems behind the FB Credit remain in place, including the outrageous 30% redemption tax, which provided FB with 18 percent of its revenue last year. The difference seems to be one of branding. An FB app can have its own virtual currency and give users a link where they can pay cash to FB (in local currencies - Yen, Euros, whatever Greece decides on, etc.) in return for the virtual coin. The coin then flows through the app back to the devs. The devs...